Non-galling bearing alloy of silver in nickel base



United States Patent 0 3,145,099 N Obi-CALLING BEARING ALLOY 0F SILVER EN NICKEL BASE William J. Parana, Waulresha, Wis, assignor to Waulresha Foundry Company, Waukesha, Wis, a corporation of Wisconsin No Drawing. Filed May 22, 1961, Ser. No. 111,469 4 Claims. (Cl. 75-470) This invention relates to an alloy using silver dispersed with other metals in a nickel base to produce a non-galling bearing material. Also involved is a method for making this and other alloys in which a eutectic is diffused to increase the alloy strength. The present alloy is particularly useful in applications requiring high wear resistance, high corrosion resistance, high temperature strength, and good machineability.

Nickel in cast or wrought form, or nickel base alloys, are Widely used in applications where corrosion resistance is desired. However, basic nickel alloys gall very badly when self-mated and are only satisfactory with a dissimilar alloy at very low bearing pressures and with adequate lubrication. Efforts to solve this problem have been many and varied. When it is essential to reduce the inherent tendency of nickel to gall and seize, the usual remedy has been to add silicon or other elements to create high hardness, or graphite or lead to provide lubrication. The low melting point of the lead precludes its use at high temperatures. Neither the graphite nor the hardeners are fully effective to prevent galling at any temperature if lubrication fails.

The object of this invention is to provide a superior bearing alloy meeting the requirements above outlined. There is a considerable demand for corrosion resistant non-galling material for use at room and high temperatures for bearing and seal applications. In particular there is a heretofore unsatisfied demand for a nickel base alloy capable of self-mating operation in a bearing without galling or seizing even at high temperatures and even if lubrication is temporarily deficient. When both of the complementary bearing elements are of identical material as is possible by reason of this invention, there is no problem of differential expansion.

A typical alloy exemplifying the invention contains ingredients substantially in the following proportions by weight:

Percent Silver 6 Zinc 8 Tin 8 Manganese 2 Carbon .20 Nickel Balance In the preferred method of producing this alloy, the nickel is placed at the bottom of a furnace and the zinc and the tin are placed at a higher level. The zinc and tin melt at temperatures greatly below the melting point of nickel. As the zinc and tin melt, they flow down over the nickel and dissolve some of the nickel. This holds the zinc and tin in solution while the remainder of the nickel is melting. This order of melting is required because zinc will vaporize with explosive force if any attempt is made to add it after the nickel is molten.

Because of the high cost of the silver, it is usually added ice only after the melt is substantially complete. Thus, if anything has gone wrong with the melt, the value of the silver will not be lost. When the silver is added, the presence of the zinc and tin will assure dispersion of the silver component uniformly throughout the alloy.

If the alloy is permitted to cool immediately, the nickelzinc eutectic tends to separate out and establish cleavage planes between the diffused bodies of silver in the alloy. A stronger alloy is achieved if the alloy is held for several hours at a temperature high enough to diffuse some or all of the eutectic into the nickel matrix. In the case of the present alloy, I prefer to hold the alloy at a temperature of at least approximately 1600 F. for a period ranging from several hours to several days. Microphotographs show that the eutectic is clearly apparent in this alloy if it is promptly cooled but has so diffused or reabsorbed as to have partially disappeared if the alloy has been held at high temperature overnight or for some longer period. The method as herein described obviously is not limited in its utility to this particular alloy but is of general application wherever a eutectic tends to separate out upon cooling.

It is preferred to use lithium in the melt as a de-oxidizing agent. The oxidized lithium then vaporizes so that it does not remain as a part of the final product. This is in accordance with conventional practice and no claim is made thereto.

Apart from the preferred method, the nature of the formula also is instrumental in this particular alloy in maintaining the silver dispersed.

The limited terminal solubilities of nickel and silver (0.102% nickel in silver at 922 C.) tend to cause the two metals to separate in the melt and to freeze in separate layers. The required dispersion of the silver in nickel base material was solved by using the mutual solubilities of silver-tin, and nickel-tin, also taking advantage of the mutual solubility of nickel-zinc and silverzinc. Balancing these elements results in dispersing the silver evenly in the nickel base.

While considerable variation in proportions is possible, it is preferred that the ingredient be kept within the ranges shown in the following table of percentages by weight:

Percent Silver 3-8 Zinc 3-9 Tin 6-9 Manganese 0-3 Carbon 05-30 Nickel Balance Nickel was selected as a base material because of its excellent corrosion resistance, availability, low cost and ease of melting. Its inherent disadvantages from the standpoint of galling or seizing are overcome by the addition of silver. Unlike the lead used in the conventional copper alloys for bearing purposes, which melts at 327 C., the silver does not melt up to 960 C. The useful temperature range of the hearing or seal is thereby greatly extended.

For high bearing loads, the carbon is increased to harden the matrix and thus increase the compressive yield strength. The inclusion of manganese is optional. It supplements the carbon in hardening and toughening the alloy. Ordinarily manganese is included because it also ment damage.

acts as a powerful deoxidizer. The higher compressive yield maintains tolerances and reduces Wear.

For relatively high temperature applications, zinc and tin are held to the minimum size of the range to reduce the eutectic on the grain boundary and minimize loss of tensile strength. However, any substantial reduction in the amount of zinc and tin reduces the amount of silver which can be properly diffused in the alloy. Accordingly, I prefer to use substantial quantities of zinc and tin and to promote diffusion by holding the alloy at high temperatures for a period of hours, as above described.

The specific alloy above defined as an embodiment of this invention has the following properties:

Tensile Percent Elongation A commercially accepted bearing bronze 8010-1O shows less than one-half as much tensile strength between room temperature and 450 F. and an average of twice as much elongation in the indicated range of temperatures and tensions.

Complementary bearings both made of my nickel-silver alloy will operate at normal pressures of 3000 p.s.i. and over, Without galling or seizing at room temperaturre to high temperature. This enables design engineers to specify very close tolerances for a gas seal or similar application without taking into account differential cofficients of expansion. In the case of using unlike materials, the designer must allow for differential expansion of unlike materials and allow for phase changes which may occur. In these instances the result is invariably a poor seal at the operating temperature or on the way up to operating temperature.

The alloy of this invention will not gall or seize under operating conditions whether lubricated or unlubricated. In the event of a lubrication failure, such as may occur in the event of a ruptured oil line, there will not be a sudden seizure which would result in excessive equip- In such a situation, the bearing will wear up to about 1200" F. but the wear will occur at so slow a rate as to allow time for gradual shut down, even if the machine is a high speed turbine or high speed water pump or other high speed equipment. At 1200 to 1500 F. mutual polishing occurs rather than Wear.

The allow of this invention has exceptional wear re- The alloy of this invention will run dry (unlubricated) against 347 stainless steel or Inconel X at 1200 F. to 1500 F. without appreciable wear. Actual dry tests were made at these temperature ranges using a 10 lb. load on a less than square surface at .090" stroke, 1000 cycles per minute for one hour. There was merely mutual polishing of the bearing surfaces without abrasion or other destructive wear either of the steel or of the alloy of this invention.

I claim:

1. A non-galling nickel-base bearing alloy adapted for self-mating as well as other bearing usage and essentially consisting of the following ingredients in the indicated ranges of percentages by weight:

Percent Silver 3-8 Zinc 39 Tin -1 69 Manganese Up to 3 Carbon Up to .3

The balance essentially nickel.

2. A bearing alloy essentially consisting of the following ingredients in the indicated ranges of percentages by weight:

Percent Silver 3-8 Zinc 3-9 Tin 69 Manganese 1-3 Carbon .05.30

The balance essentially nickel.

3. A bearing alloy essentially consisting of substantially the indicated percentages by weight of the following ingredients:

Percent Silver 6 Zinc 8 Tin 8 Manganese 2 Carbon .20

The balance essentially nickel.

4. An alloy according to claim 1 wherein the silver is in partial solution in the zinc and in partial solution in the tin, the tin and zinc being in mutual partial solution in each other to effect substantially uniform dispersion of the silver through the alloy.

References Cited in the file of this patent UNITED STATES PATENTS 724,524 Telden Apr. 7, 1903 1,683,749 Winslow Sept. 11, 1928 1,757,508 Baker May 6, 1930 1,873,155 Scharnow Aug. 23, 1932 1,925,978 Cooper Sept. 5, 1933 2,159,763 Hensel May 23, 1939 2,261,553 Lakatos Nov. 4, 1941 2,358,326 Hensel Sept. 19, 1944 2,585,393 Lyle Feb. 12, 1952 2,911,297 Dusseldorf Nov. 3, 1959 3,024,109 Hoppin et al Mar. 6, 1962 OTHER REFERENCES Silver in Industry, by L. Addicks, Reinhold Publishing Corp., 1940, pages -96 

1. A NON-GALLING NICKEL-BASE BEARING ALLOY ADAPTED FOR SELF-MATING AS WELL AS OTHER BEARING USAGE AND ESSENTIALLY CONSISTING OF THE FOLLOWING INGREDIENTS IN THE INDICATED RANGES OF PERCENTAGES BY WEIGHT: 